/Engine/Source/Runtime/Core/Public/Async/TaskGraphInterfaces.h
"Complete" the event. This grabs the list of subsequents and atomically closes it. Then for each subsequent and for each item in "NewTasks" it reduces the number of prerequisites outstanding and if that drops to zero, the task is queued.
void DispatchSubsequents ( [TArray](API\Runtime\Core\Containers\TArray)< [FBaseGraphTask](API\Runtime\Core\Async\FBaseGraphTask) * > & NewTasks, [ENamedThreads::Type](API\Runtime\Core\Async\ENamedThreads__Type) CurrentThreadIfKnown, bool bInternal )